A screen for new modulators of the TRAIL-induced apoptosis pathway. 12,190 siRNAs targeting 6,095 genes were screened in duplicate for genes affecting sensitivity to TRAIL induced pathway (see materials and methods). a) Distribution of scores for sample siRNAs. Survival after treatment was median normalised by plate, a z-like score calculated using median and median absolute deviation and the minimum of two replicates was selected for each siRNA (see methods and ). This score represents a normalized measure of the effect of a particular siRNA compared to the majority of siRNAs and is robust to outliers. b) Boxplot of scores for each of groups of controls used in the screen. NoT = Not Transfected c) Induction of Caspase-3/7 activity after 6 hrs treatment with 0.5 μg/ml TRAIL after knock-down of confirmed hit genes with multiple siRNAs compared to induction in cells transfected with negative control siRNA. Error bars represent 1 standard deviation (n = 3) all results are significant from negative control (P < 0.05, Students' t-test).